The invention described herein may be manufactured and used by or for the Government of the United States for all governmental purposes without the payment of any royalty.
In my above-identified U.S. Patent there is disclosed an arrangement for passively determining the location of a fixed-position signal emitter from a moving platform such as an aircraft. The location algorithm described in this issued patent is based on the time difference of arrival (TDOA) of a signal received at different locations on the moving platform from the emitter being located in order to determine a vectorial or azimuthal position of the signal emitter with respect to the moving platform. This location algorithm is also based on a rate of change of the TDOA data to determine the distance between the moving platform and the signal emitter. The algorithm of this issued patent may therefore be considered to be based on the concept of two unknowns being determined by solving two different equations i.e., the unknowns of azimuth and distance being determined from measurement of signal travel time difference and rate of change of signal travel time difference.
If the signal to be located is however moving in position rather than being stationary the algorithm of this issued patent is unable to provide a location of the signal emitter because an additional unknown is added to the xe2x80x9cequationsxe2x80x9d being solved. In this moving signal source instance it can be readily appreciated that the rate of change of travel time difference is determined by both signal emitter movement and platform, i.e., aircraft movement. In order to determine instantaneous emitter location in this moving emitter instance it is apparent that some additional input of data is needed in the location algorithm. As disclosed in the material following, this need for additional input data is easily met and met in a manner that is at first blush strikingly similar to the data sources used in my issued patent but is however, upon system consideration, quite different with respect to the data sources of the issued patent.
The present invention provides an arrangement for determining the location of, and if desired the velocity of, a moving signal emitter source while the source is observed from a moving platform such as an aircraft. The invention continues the capabilities disclosed in my above-referenced previous patent of being capable of making this location determination during a short time interval, from a short duration emission of the moving emitter and with a system having self calibrating capability.
It is therefore an object of the present invention to provide a moving emitter location system operable from a moving platform such as an aircraft.
It is another object of the invention to provide a moving emitter location system based on the use of easily obtained input signal information.
It is another object of the invention to provide a time based moving platform-received unambiguous locating system for a distant signal source that is also moving.
It is another object of the invention to provide a time based moving platform-received unambiguous locating system providing angle and range information relative to a distant moving target.
It is another object of the invention to provide a time based moving platform-received unambiguous locating system providing angle and range information relative to a distant moving target through use of received radio frequency signals.
It is another object of the invention to provide a moving emitter location system that is self-calibrating in nature.
It is another object of the invention to provide a moving emitter location system based on the use of three signals of somewhat similar nature obtained from displaced signal collectors located on a moving vehicle.
It is another object of the invention to provide a moving emitter location system that is based on the differing arrival times of a radio frequency signal at displaced antennas on a vehicle.
It is another object of the invention to provide a moving emitter location system that is based on the differing arrival times of a radio frequency signal at displaced antennas located on an aircraft.
It is another object of the invention to provide a moving emitter location system based on the differing arrival times of a radio frequency signal at displaced antennas located on a moving aircraft.
It is another object of the invention to identify the location of for example a moving random pulse-to-pulse frequency agile radar emission source from a moving platform.
It is another object of the invention to provide a moving emitter location system based on the use of large baseline signal interferometers.
It is another object of the invention to provide a distant signal source locating arrangement supported by a propagation time-based mathematical algorithm.
These and other objects of the invention will become apparent as the description of the representative embodiments proceeds.
These and other objects of the invention are achieved by passive moving signal source relative-locating apparatus comprising the combination of:
a time difference of arrival interferometer algorithm airborne signal locating system disposed within signal reception range of said moving signal source;
multi-channel signal reception port apparatus disposed in physically segregated locations attending an aircraft carrying said airborne signal locating system;
said multi-channel signal reception apparatus including first signal reception port apparatus disposed on a first physical portion of said aircraft and connected with a receiver apparatus within said aircraft by a first signal delay-calibrated signal transmission path;
said multi-path signal reception apparatus also including second signal reception port apparatus disposed proximate said aircraft and connected with said receiver apparatus within said aircraft by a second signal delay-calibrated signal transmission path;
said multi-path signal reception apparatus also including third signal reception port apparatus disposed proximate said aircraft and connected with said receiver apparatus within said aircraft by a third signal delay-calibrated signal transmission path;
said receiver apparatus within said aircraft including time difference of arrival measurement apparatus selectively connecting with said first, second and third signal reception port apparatus by said first path, second path and third path signal delay-calibrated signal transmission paths respectively;
said time difference of arrival measurement apparatus including angular measurement computation apparatus determining from selected pairs of measured time difference of arrival signals first, second and third angular relationships respectively between said first, second and third signal reception ports of said moving aircraft carrying said airborne signal locating apparatus and said moving airborne signal source;
said time difference of arrival measurement apparatus further including distance computation apparatus determining from selected pairs of said first, second and third angular relationships a straight line measurement between said moving aircraft carrying said airborne signal locating apparatus and said moving airborne signal source.